Muon Wobble mysteriously deepens when Fermilab reaches its precise target

After six years of meticulous measurements, Fermilab’s scientists have made their last statement on one of the most confusing mysteries in physics: How much Moon sways in a magnetic field?

To be precise, the answer is the full target per billion dollar, exceeding its original target and representing the most accurate measurement ever. However, this extraordinary precision does not solve the mystery, but emphasizes the growing gap in the theoretical physics community about the actual meaning of numbers.

The MUON G-2 experiment ended its data collection in 2023, focusing on a fundamental particle called MUON. It can be considered as a cousin with a heavier electron, about 200 times but shares the same charge. Like a tiny rotating top, Moos sways when placed in a magnetic field, and the speed of the sway depends on what characteristics should be predictable using our best theory of particle physics: the standard model.

A century-old puzzle becomes more accurate

“For more than a century, the G-2 has been teaching us about the nature of nature,” said Lawrence Gibbons, a Cornell professor and analysis coordinator. “It’s exciting to add an exact measure that I think will last for a long time.”

The name of the experiment comes from a simple relationship. About 100 years ago, physicists predicted that the number of G-factors would be equal to 2. But the experiment always shows a slightly different amount, which is called a magnetic anomaly, calculated as (G-2)/2.

This tiny deviation encodes the effects of each particle in the standard model, creating what physicists call a “strict benchmark” for understanding basic physics. When a previous version of the experiment was run at Brookhaven National Laboratory in the early 2000s, it hints at a discrepancy that could indicate the presence of undiscovered particles.

Great Theory Split

But this is where the story brings unexpected changes. Although Fermilab is perfecting their measurements, theoretical physicists are struggling to meet their own challenge: two different methods of calculating Muon’s swing should give different answers.

Traditional methods use input data from other experiments. A newer calculation method depends largely on computer simulation. Latest calculations using computational techniques are closer to experimental actual measurement methods, thus reducing the obvious differences that once inspired physicists who hoped for new signs of physics.

“Moon’s anomaly magnetic moment, or g-2, is important because it provides a sensitive test of the standard model of particle physics,” said Regina Rameika, deputy director of the U.S. Department of Energy Office of High Energy Physics. “This is an exciting result, and it’s great to see an experiment that achieves definite purpose with precise measurements.”

Unusual cooperation

What makes this experiment particularly outstanding is not only its accuracy, but also the diverse expertise required to achieve this. Unlike typical high-energy physics experiments, MUON G-2 brings together scientists from multiple disciplines.

“The experiment is very strange because it has very different compositions,” said Marco Incagli, a physicist at the Italian National Institute of Nuclear Physics, Pisa, co-spokeshop of MUON G-2. “This is indeed done by collaboration between communities that usually work on different experiments.”

176 scientists from 34 institutions include not only particle physicists, but also accelerator physicists, atomic physicists and nuclear physicists. The experiment required the move of Brookhaven’s huge magnetic storage ring from New York to Illinois in 2013, a logistical feat involving careful transport of 50-foot-long superconducting magnets.

Key Discovery

The final experimental measurement achieved several milestones:

• Accuracy is $12.7 billion, exceeding the original design target of $14 billion
• Analyze the highest quality data from 2021-2023
• Compared with the 2023 results, the dataset size is more than three times
• Confirm previous measurements with unprecedented accuracy

What will happen next?

Although the main analysis concluded, collaboration has not yet completed mining of data. Future research will examine the electrically dipole moments of MUON and test the basic symmetry in physics, which can reveal new insights about the fundamental structure of the universe.

“It’s a very exciting moment because we’re not only achieving the goals, but we’re beyond them, which isn’t easy for these precise metrics,” said Peter Winter, a physicist at Argonne National Laboratory.

Future experiments on Japanese particle accelerator complexes may take another measurement in the early 2030s, although initially the accuracy is lower than that of Fermirab. Meanwhile, the theoretical physics community continues to work hard to resolve the differences between the two computational methods.

The question remains: Does Muon’s swing reveal cracks in our understanding of fundamental physics, or does it just confirm how good our current theories are? The answer may depend on which theoretical calculations prove to be correct – this debate is that this exact measurement is more urgent than ever.